JOHANNESBURG, South Africa (AP)  President Bush's pledge to give $15 billion for AIDS relief in Africa and the Caribbean was hailed by a U.N. official Wednesday as a "dramatic signal" the United States was ready to confront the pandemic, while others working with the devastating illness said far more was needed. (Related story: Bush defies conservatives, drug companies with AIDS plan)

An estimated 29.4 million people in sub-Saharan Africa are infected with HIV, out of 42 million afflicted worldwide. Only several thousand people across the continent have access to lifesaving AIDS medicine that is readily available in developed countries.

"It gives leverage to activists everywhere to keep the pressure on. It transforms the response. It opens the floodgates of hope," Stephen Lewis, the U.N. special envoy for HIV/AIDS in Africa, said of the Bush promise during a news conference in Johannesburg.

Many Africans have no health care at all and cannot even get medicine to fight ailments such as pneumonia and tuberculosis that prey on those with HIV. There are huge shortages of doctors, nurses and clinics.

In his State of the Union address, Bush asked Congress to provide $15 billion over five years to provide AIDS drugs to 2 million people, help prevent 7 million new infections, and care for those infected with and children orphaned by the virus.

He called the money a "work of mercy" that would save the lives of millions of people in Africa and the Caribbean.

Bush's pledge should also put pressure on other developed countries to increase their contributions to AIDS treatment, Lewis said.

Others specialists were more reserved.

"We appreciate the move and the gesture, but will it be enough? We don't even know how the money will be used and who will get what," said Najib Balala, Kenya's social services minister. "How do we all share this money."

Mark Heywood, secretary of the Treatment Action Campaign, a South African AIDS activist group, called the U.S. pledge "paltry" compared to the money going to the buildup of forces in the Gulf.

"What's being spent on war preparations shows that there are substantial amounts of money floating around in the world that could be targeted at the world's real problems," Heywood said.

Experts estimate rich nations need to spend at least $10 billion a year to make any impact in the fight against HIV in the developing world, but only spent $2.8 billion last year.

Some activists were concerned that the bulk of the money would be given directly to African governments — many of which have squandered previous aid — instead of to the U.N.-administered global fund against AIDS.

That fund gives more targeted grants and works to build up countries' health-care systems, increase prevention efforts and expand access to anti-AIDS drugs.

According to the White House, a total of $1 billion of the pledged money will go to the fund over five years. The remainder will go to private groups and governments to fund laboratories, train health workers and provide tests, education and medicine.

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